The use of single-wall carbon nanotubes (SWNTs) in manufacturing and biomedical applications is increasing at a rapid rate; however data on the effects of a potential environmental release of the materials remain sparse. In this study, soils with either low or high organic matter contents as well as pure cultures of E. coli are challenged with either raw As-Produced SWNTs (AP-SWNTs) or SWNTs functionalized with either polyethyleneglycol (PEG-SWNTs) or m-polyaminobenzene sulfonic acid (PABS-SWNTs). To mimic chronic exposure, the soil systems were challenged weekly for six weeks; microbial activities and community structures for both the prokaryote and eukaryote community were evaluated. Results show that repeated applications of AP-SWNTs can affect microbial community structures and induce minor changes in soil metabolic activity in the low organic matter systems. Toxicity of the three types of SWNTs was also assessed in liquid cultures using a bioluminescent E. coli-O157:H7 strain. Although decreases in light were detected in all treated samples, low light recovery following glucose addition in AP-SWNTs treatment and light absorption property of SWNTs particles suggest that AP-SWNTs suppressed metabolic activity of the E. coli, while the two functionalized SWNTs are less toxic. The metals released from the raw forms of SWNTs would not play a role in the effects seen in soil or the pure culture. We suggest that sorption to soil organic matter plays a controlling role in the soil microbiological responses to these nanomaterials.
"Compared with pure cultures and wastewater systems, the soil environment is much more complex and uncontrolled. When graphene enters the soil, it may interact with organic matter or clay minerals present in the soil , stabilizing graphene and making it less bioavailable, which would mitigate the effect of graphene on microbial communities. On the contrary, dissolved organic matter (DOM) might promote the mobility and bioavailability of graphene by acting as natural surfactants . "
[Show abstract][Hide abstract] ABSTRACT: Production and use of carbon nanotubes (CNTs) will unavoidably lead to their disposal in the environment. To assess the risk associated with their release, an understanding of their mobility and ultimate fate is essential. To date, however, relatively little research has been conducted on the fate of CNTs in the environment. In this study, phase distributions of multi-walled carbon nanotubes (MWCNTs) between water and soils were determined by classical laboratory batch experiments and compared with values estimated from several prediction models. Aggregation and subsequent sedimentation appeared to be an important process governing the phase distribution of MWCNTs between water and soils. In this respect, corrected LogK oc was calculated by excluding the mass of settled MWCNTs and the values were from 3.73 to 4.64. Octanol-water partition coefficient (K ow) of MWCNTs was also determined to predict the soil sorption property. The LogK oc values estimated from prediction models were from 1.12 to 2.31. These results indicate that the K ow alone may not be an appropriate predictor of K oc for MWCNTs and other predictors or approaches should be explored to accurately estimate the potential mobility of MWCNTs in the environment.
[Show abstract][Hide abstract] ABSTRACT: Recent developments in nanotechnology may lead to the release of nanomaterials into the natural environment, such as soils, with largely unknown consequences. We investigated the effects of single-walled carbon nanotubes (SWCNTs), one of the most widely used nanomaterials, on soil microbial communities by incubation of soils to which powder or suspended forms of SWCNTs were added (0.03 to 1mgg(-1) soil). To determine changes in soil microbial community composition, phospholipid fatty acid (PLFA) profiles were analyzed at 25th day of the incubation experiment. The biomass of major microbial groups including Gram-positive and Gram-negative bacteria, and fungi showed a significant negative relationship with SWCNT concentration, while the relative abundance of bacteria showed a positive relationship with SWCNT concentration. Furthermore, soils under distinct concentrations of SWCNT treatments had PLFA profiles that were significantly different from one another. Our results indicate that the biomass of a broad range of soil microbial groups is negatively related with SWCNT concentration and upon entry into soils, SWCNTs may alter microbial community composition. Our results may serve as foundation for scientific guideline on regulating the discharge of nanomaterials such as SWCNTs to the soil ecosystem.
Science of The Total Environment 08/2013; 466-467C:533-538. DOI:10.1016/j.scitotenv.2013.07.035 · 4.10 Impact Factor
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